1. Field of the Invention
The present invention generally relates to a vehicle-applied monitoring system and more particularly, to a vehicle-applied rear-and-side monitoring system which takes an image of a rear-and-side view of a running vehicle by means of an imaging apparatus such as a small-sized Charge Coupled Device (hereinafter CCD) mounted on the vehicle, detects a following vehicle in a the taken image, and gives a driver an alarm or the like indicating the approach of the following vehicle.
2. Description of Related Art
There exists dangerousness of a big traffic accident due to a dead angle area when a running vehicle changes a lane. For example, if a driver of a preceding vehicle executes a lane change without recognizing a following vehicle having entered the dead angle area, such a traffic accident as a collision would happen.
In order to prevent the above-described accident or dangerous situation, technology to make a driver accurately and surely recognize the existence of the following vehicle has been proposed.
For example, Japanese Patent Application Laid-open No. 1-189289 (hereinafter JP ""289) discloses a vehicle information-display system which makes a driver recognize a vehicle running on th neighboring lane or at the back of the own vehicle. The prior art disclosed in JP ""289 can makes a driver recognize a vehicle running on the neighboring lane or at the back of the own vehicle by taking an image of a rear-and-side view of the own vehicle with a camera and by showing the taken image on a monitoring display.
With respect to the above prior art, however, a driver has to watch the monitoring display carefully while driving so as to check the existence of a following vehicle, and further it would be difficult to judge whether the following vehicle is approaching the own vehicle or not.
Therefore, a vehicle-applied rearward monitoring system and vehicle-applied rearward monitoring method using this system have been proposed, wherein a relative speed, a relative distance, and/or a relative position between the own vehicle and the following vehicle running at the back of the own vehicle or on the neighboring lane are obtained by calculating a infinity point (or a disappearance point) which is generally called xe2x80x9cFocus of Expansionxe2x80x9d (hereinafter FOE), which FOE is a point where every points of an image taken by a video camera converge, by extracting a characteristic point from an image recognized as the following vehicle, and by calculating movement of the characteristic point. Hereinafter, the movement of the characteristic point is called optical flow.
Here, a rear monitoring method with the above conventional vehicle-applied rearward monitoring system will be briefly described below with reference to FIGS. 9A and 9B.
FIGS. 9A and 9B are schematic views showing an example of sequential images of a rear-and-side view taken by a rearward monitoring camera, i.e., the image taking means, backward-lookingly mounting on a rear portion of the own vehicle and imaged on the image plane 1100 of an image sensor such as a CCD image sensor of the camera. In FIGS. 9A and 9B, the following vehicle 1101 is passing the own vehicle. Here, references numerals 1205 and 1207 indicate lane markings on the road.
First, referring to FIG. 9A, an image of the following vehicle 1101 is recognized in an image of a rearward view in the image plane 1100.
Conventionally, a boundary, i.e., an edge, between an image of the following vehicle 1101 and images of the others such as the road, a background and the like (not shown), which are imaged on the image place 1100, is recognized by making use of a luminance difference therebetween.
After recognition of the edge of the image of the following vehicle 1101, the characteristic point A fitting to predetermined conditions is extracted by recognizing the edge or an area within the edge.
Further, at the next time-point, a corresponding point Axe2x80x2 is detected to form an optical flow connecting the points A and Axe2x80x2.
The degree of dangerousness of movement of the following vehicle 1101 is judged on the basis of the optical flow of the following vehicle 1101. In case the following vehicle 1101 has been calculated to be in a dangerous position, an alarm is given to a driver to prevent the danger if fa direction indicator is put on.
With respect to the above conventional vehicle-applied rearward monitoring system, however, there is drawback mentioned below.
Here, FIG. 7 is a schematic view showing an example of relative position between own vehicle 1103 running on the road 1202 and provided with the conventional vehicle-applied rearward monitoring system and the following vehicle 1101. Reference numeral 1201 indicates a side area band of the own vehicle 1103. And, reference numerals 1203 and 1204 indicate left and right traffic lanes, respectively, and reference numerals 1205, 1206, and 1207 indicate lane markings in the road 1202. Further, reference character xcex8 indicates an image taking angle.
Referring to FIG. 7, in case that the following vehicle 1101 has entered a dead angle area 1200 of an image taking means 1104 mounted on the own vehicle 1103, the following vehicle 1101 cannot be detected or calculated with the conventional vehicle-applied rearward monitoring system.
If the own vehicle 1103 executes a lane change when the following vehicle 1101 has entered the dead angle area 1200, a big traffic accident, such as a collision, would happen.
In view of the foregoing, an object of the present invention is to provide a vehicle-applied rear-and-side monitoring system which can accurately and surely detect and calculate the existence of the following vehicle having entered a dead angle area of the own vehicle.
In order to achieve the above-described object, as a first aspect of the present invention, a vehicle-applied rear-and-side monitoring system of the present invention includes: an image taking means for taking an image of a rear-and-side view of an own vehicle being running on a lane; and a characteristic point extracting means for extracting at least one point as a characteristic point from an image of a following vehicle contained in a first image, taken at a first time-point, of the rear-and-side view, the following vehicle being running at the back of the own vehicle on the lane or on a neighboring lane of the lane; a corresponding point detecting means for detecting a corresponding point, corresponding to the characteristic point, in a second image taken at a second time-point following the first time-point; an optical flow forming means for forming an optical flow of the characteristic point of the following vehicle from a vector connecting the characteristic point and the corresponding point; and a dead angle area located vehicles-distance calculating means for calculating at least any one of a vehicles-distance between the own vehicle and the following vehicle and a relative position therebetween after a time-point of disappearance of the optical flow outside an image place of the image taking means on the basis of the optical flow formed just before the disappearance, wherein an approaching degree of the following vehicle being running at the back of the own vehicle on the lane or on the neighboring lane is monitored.
According to the above-described structure, by showing the calculated results of the vehicles-distance or the relative position on an image place of the displaying means using, for example, a liquid crystal display panel, a driver can surely recognize an existence of the following vehicle having entered the dead angle area of the own vehicle.
As a second aspect of the present invention, in the structure with the above first aspect, the dead angle area located vehicles-distance calculating means considers that the optical flow of the characteristic point of the following vehicle having arrived at a predetermined peripheral area of the image plane of the image taking means at the first time-point disappears from the image plane at the second time-point, uses the optical flow at the first time-point as the optical flow formed just before the disappearance, and calculates at least any one of the vehicles-distance and the relative position after the first time-point or after the second time-point.
According to the above-described structure, since the dead angel area located vehicles-distance calculating means considers that the optical flow having arrived at the predetermined peripheral area of the image plane will disappear from the image plane at the next time-point and continues the calculation, a driver can surely recognize an existence of the following vehicle having entered the dead angle area of the own vehicle.
As a third aspect of the present invention, the vehicle-applied rear-and-side monitoring system with the above first aspect further includes a dangerousness judging means for judging degree of danger of contact or collision with the following vehicle on the basis of the vehicles-distance and the relative position having been calculated by the dead angle area located vehicles-distance calculating means.
According to the above-described structure, since the dangerousness judging means judges degree of danger of contact or collision with the following vehicle every moment on the basis of the vehicles-distance and the relative position having been calculated by the dead angle area located vehicles-distance calculating means, the danger of contact or collision can be prevented by warning a driver with a display, an alarm buzzer, or the like.
As a fourth aspect of the present invention, the vehicle-applied rear-and-side monitoring system with the above first aspect further includes an alarm giving means for giving an alarm indicating danger by means of at least any one of auditory information and optical information in case that an operation for activating a direction indicator provided on the own vehicle is executed when the vehicles-distance or the relative position having been calculated by the dead angle area located vehicles-distance calculating means is within a predetermined range.
According to the above-described structure, though execution of a lane change or the like by the own vehicle in a state that the following vehicle has entered the dead angle area of the own vehicle would cause such a big accident as a collision of the own vehicle against the following vehicle, since the alarm giving means gives a driver an alarm indicating danger by means of auditory or optical information in case that an operation for activating the direction indicator provided on the own vehicle is executed when the following vehicle is in the dead angle area, such a big accident as a collision can be prevented.
As a fifth aspect of the present invention, in the structure with the above second aspect, the dead angel area located vehicles-distance calculating means calculates neither the vehicles-distance nor the relative position after the first time-point or after the second time point in case that the optical flow having arrived at the predetermined peripheral area of the image plane of the image taking means at the first time-point has a directional component corresponding to a direction within a range between horizontal and upward-vertical in the rear-and-side view, and calculates at least any one of the vehicles-distance and the relative position after first time-point or after the second time-point in case that the optical flow having arrived at the predetermined peripheral area of the image plane of the image taking means at the first time-point has a directional component corresponding to a direction within a range between horizontal (not included) and downward-vertical in the rear-and-side view.
According to the above-described structure, since the dead angle area located vehicles-distance calculating means executes the calculation only when the following vehicle is certainly entering the dead angle area, a driver can recognize dangerousness correctly.
As a sixth aspect of the present invention, the vehicle-applied rear-and-side monitoring system with any one of the above first to fifth aspects further includes a second alarm giving means for giving an alarm indicating danger of a lateral collision by means of at least any one of auditory information and optical information in case that an operation for lane change is executed within a predetermined time period from the time-point of the disappearance of the optical flow from the image plane of the image taking means.
According to the above-described structure, since the second alarm giving means does not take account of the vehicles-distance between the own and following vehicles and the relative position therebetween, calculation can be simplified and the alarm can be utilized as provisional alarm, for example.
As a seventh aspect of the present invention, a vehicle-applied rear-and-side monitoring system of the present invention includes: an image taking means for taking an image of a rear-and-side view of an own vehicle traveling in a lane; a characteristic point extracting means for extracting at least one point as a characteristic point from an image of a following vehicle contained in a first image, taken at a first time-point, of the rear-and-side view, the following vehicle traveling at the rear of the own vehicle in the lane or in a neighboring lane; a corresponding point detecting means for detecting a corresponding point, corresponding to the characteristic point, in a second image taken at a second time-point following the first time-point; an optical flow forming means for forming an optical flow of the characteristic point of the following vehicle from a vector connecting the characteristic point and the corresponding point; and a dead angle area located vehicles-distance calculating means for calculating at least any one of a vehicles-distance between the own vehicle and the following vehicle and a relative position therebetween after a time-point of disappearance of the optical flow outside an image plane of the image taking means on the basis of a plurality of optical flows including said optical flow formed just before said disappearance, wherein an approaching degree of the following vehicle being running at the rear of the own vehicle in the lane or in the neighboring lane is monitored.
According to the above-described structure, by showing the calculated results of the vehicles-distance or the relative position on an image plane of the displaying means using, for example a liquid crystal display panel, a driver can more surely recognize an existence of the following vehicle having entered the dead angle area of the own vehicle.
As an eighth aspect of the present invention, in the structure with the above seventh aspect, the dead angle area located vehicles-distance calculating means calculates the vehicles-distance or the relative position on the basis of a relative speed expected from a relative acceleration obtained from relative speeds corresponding to the plurality of optical flows.
According to the above-described structure, the dead angle area located vehicles-distance calculating means can calculate the vehicles-distance or the relative position more precisely.
As a ninth aspect of the present invention, in the structure with the above eight aspect, the dead angle area located vehicles-distance calculating means calculates the vehicles-distance or the relative position on the basis of both the expected relative speed and a relative traveling direction, of a second vehicle relative to a first vehicle, expected from direction change values of the plurality of optical flows.
According to the above-described structure, the dead angle area located vehicles-distance calculating means can calculate the vehicles-distance or the relative position still more precisely.
The above and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.